Path: csiph.com!news.freedyn.net!aioe.org!gothmog.csi.it!bofh.it!news.nic.it!robomod From: Stephen Boyd Newsgroups: linux.kernel Subject: Re: [PATCH] extcon: Add support for qcom SPMI PMIC USB id detection hardware Date: Thu, 30 Jun 2016 03:10:01 +0200 Message-ID: References:

X-Original-To: Chanwoo Choi , Rob Herring Dkim-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=JzP4oF0IAOICVYGDc6nyc7oDXHvdsb+neqfZ4dg+P0E=; b=D/lAt9LR8lfF2YvO7ljAAF5rbBXN/qDqdvVSuyHAKWtXwnxu6y0pSFcLXj4oVLKBdo 9T16+Zm0/Fap89KDuAsiDS3xGYSPX4vhcrFlIuw8j+6GosBZL2BtkMGdRwcpvlcUtjwA Tb3sadERahcrZCwuP7u9+YC25dqElqcNfYBYw= X-Google-Dkim-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=JzP4oF0IAOICVYGDc6nyc7oDXHvdsb+neqfZ4dg+P0E=; b=S+ROz6+rikIIEEFqmIO5eWsvaXOBOVyBXSbiBpzime91ziE10oYq8NwYrsObqrdMwF /7GoecS+JdCQ5dlgmvr/IztQOLHjxIM6JiPZlUbP6xgRSRyoIv6MKpZQ6vdZzRTdef73 PPvB5t39NSvQehi6qzSaggBsGsjLcX9wp1jLLxjCj0qankUkzEO2rf70KpYsH1yljVnP jPNMvCSDWf2f/+s7vQQfSogjYOM1jw3IHpXM66UfIRpqwOQGV4EH7rWJ2QHiaS8ccg43 gZeh1c+j5FfW0tmnMLYVqibbDirT8MQupFSVcIhXMz2BmuvqeXeP2YzANz3supOYcg6P Qi/g== X-Gm-Message-State: ALyK8tJrHD6QyDzkFD8YMpFMN4Ji7py9ryCaolXOJdufEEszLe0vA929UERL/YgxqK8csIuAjHZfRSTIZzc0yDN1 X-Received: by 10.176.64.37 with SMTP id h34mr5561226uad.112.1467248695351; Wed, 29 Jun 2016 18:04:55 -0700 (PDT) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: robomod@news.nic.it List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Approved: robomod@news.nic.it Lines: 77 Organization: linux.* mail to news gateway X-Original-Cc: Chanwoo Choi , linux-arm-msm@vger.kernel.org, linux-kernel , linux-arm-kernel , Roger Quadros X-Original-Date: Wed, 29 Jun 2016 18:04:54 -0700 X-Original-Message-ID: X-Original-References: <20160626055647.18898-1-stephen.boyd@linaro.org> <146705470025.30684.13257433085055355379@sboyd-linaro> <146715115921.31418.2315766296233007937@sboyd-linaro> <577369F5.8040907@samsung.com> <146722608622.16253.4347418438203284037@sboyd-linaro> <57746935.4030107@samsung.com> X-Original-Sender: linux-kernel-owner@vger.kernel.org Xref: csiph.com linux.kernel:1434136 On 29 June 2016 at 17:35, Chanwoo Choi wrote: > On 2016년 06월 30일 03:48, Stephen Boyd wrote: >> Quoting Chanwoo Choi (2016-06-28 23:25:57) >>> On 2016년 06월 29일 06:59, Stephen Boyd wrote: >>>> Quoting Chanwoo Choi (2016-06-28 05:06:48) >>>>> 2016-06-28 4:11 GMT+09:00 Stephen Boyd : >>>>>> Quoting Chanwoo Choi (2016-06-26 04:20:43) >>>>>>> 2016-06-26 14:56 GMT+09:00 Stephen Boyd : >>>>>>>> +PROPERTIES >>>>>>>> + >>>>>>>> +- compatible: >>>>>>>> + Usage: required >>>>>>>> + Value type: >>>>>>>> + Definition: Should contain "qcom,pm8941-misc"; >>>>>>>> + >>>>>>>> +- reg: >>>>>>>> + Usage: required >>>>>>>> + Value type: >>>>>>>> + Definition: Should contain the offset to the misc address space >>>>>>> >>>>>>> 'reg' property is used on extcon-qcom-spmi-misc.c? >>>>>>> I think that you don't need to include this property. >>>>>> >>>>>> No it isn't used in the driver right now, but there is a register offset >>>>>> for this module and there are registers that can be read/written in this >>>>>> module. I'd like to keep it as required so we can easily read the >>>>>> registers in the future if needed. >>>>> >>>>> OK. >>>>> But, If you want to remain the reg property, you should add the code to get >>>>> the register offset by using OF functions. This patch don't include the OF >>>>> function to handle it. >>>>> >>>> >>>> Sorry I don't follow the argument. I've put the reg property here for >>>> future proofing so that the binding doesn't have to change in backwards >>>> incompatible ways in the future if we do need to get the property later. >>> >>> I don't mention that 'reg' property should be removed. >> >> Ok good. We need to keep reg property as this device is on a bus that >> uses reg property for addressing. >> >>> Just if you want to remain it, you should add some codes as following: >>> For exmaple, >>> - of_get_address() to get the address information from device-tree. >>> >>> If documentation include the some properties, you should add the handling code >>> in device driver. When you add the code to get the offset from device-tree, >>> it doesn't influence the some behavior in the future. >> >> Sorry I don't understand that argument. We can put properties into >> bindings and not use them in drivers if there isn't any immediate need >> to use them. >> >> From what I can tell you're suggesting we call of_get_address() in the >> driver and then do nothing with the value of the property? Is that just >> to check that the node is compliant with the binding and actually has a >> reg property? We don't add code in the kernel to check dts compliance, >> so I'm not inclined to do anything more here. > > I don't agree. > > When he DT binding document include the 'reg' property. > But, the device driver don't include any code to handle the 'reg' property > (just to get the offset). It is obviously wrong. > > It is just basic principle to write the Device-tree binding document. > > Other developer who don' know the history about 'reg' property > would be embarrassed. Why don't extcon driver include the code to > handle the 'reg' property? There is no method to explain it. > Perhaps Rob can explain why having a reg property is required for a bus that has #address-cells=<1> even though the device driver isn't using the reg property.